BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

GMAT Prep 2- Quant 4

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |
Legendary Member
Posts: 621
Joined: Wed Apr 09, 2008 7:13 pm
Thanked: 33 times
Followed by:4 members

by vittalgmat » Sat Apr 11, 2009 3:48 pm
E.
I am not sure of this.
let me attempt. Pls jump in and correct me.

stmt 1: y = x +1
stmt 2: y = x^2 +1

It is clear that each stmt independently is insufficient.

lets try to combine them.
I can see that x = 0 and x = 1 satisfies both the stmts.

So it is insufficinet. Ans is E

Alternately, one can try to add or subtract stmts 1 and 2 to get x and y.


Ht Helps
-V
Top
Senior | Next Rank: 100 Posts
Posts: 38
Joined: Fri Feb 20, 2009 8:45 am
Thanked: 5 times

answer E)

by syr » Sat Apr 11, 2009 5:08 pm
xy = ?

Take stmt 1)

y = x + 1
multiply by x
xy = x^2 + x
Insuffcient since we dont know x

Take stmt 2)

y = x^2 + 1
multiply by x
xy = x^3 + x
Insufficient

Taking both together we can equate
x^2 + x = x^3 + x
solving gives
x = 0 or 1
hence, xy = 0 or xy = 2
so C) insufficient

Hence E)

Solving by forming equations gives sure shot answer and sometimes, according to me, faster.

Any other better methods ?
Top
Legendary Member
Posts: 621
Joined: Wed Apr 09, 2008 7:13 pm
Thanked: 33 times
Followed by:4 members

Re: answer E)

by vittalgmat » Sat Apr 11, 2009 5:53 pm
syr wrote:xy = ?

Take stmt 1)

y = x + 1
multiply by x
xy = x^2 + x
Insuffcient since we dont know x

Take stmt 2)

y = x^2 + 1
multiply by x
xy = x^3 + x
Insufficient

Taking both together we can equate
x^2 + x = x^3 + x
solving gives
x = 0 or 1
hence, xy = 0 or xy = 2
so C) insufficient

Hence E)

Solving by forming equations gives sure shot answer and sometimes, according to me, faster.

Any other better methods ?
Thanks Syr,
Ur soln is better.
Top
Legendary Member
Posts: 2467
Joined: Thu Aug 28, 2008 6:14 pm
Thanked: 331 times
Followed by:11 members

by cramya » Sat Apr 11, 2009 6:47 pm
Nice solutions.

y= x+1
y = x^2+1

x+1 = x^2+1

x^2-x = 0
x ( x-1) = 0

x=0 x=1

Two possible solutions that change xy.

INSUFF
Regards,
CR
Top
Post new topic Post Reply
• Page 1 of 1